1. Field of the Invention
The present invention relates to catheter systems, and in particular, to an automated balloon catheter fluid purging system.
2. Description of the Related Art
A typical industrial fluid purging system normally uses a pressure sensor (i.e. pressure switch, pressure transducer, etc.) to detect the fluid pressure within the pressurized chamber, and relieves high pressure directly from the pressurized chamber through an exhaust valve. This typical industrial fluid purging system does not incorporate a relief valve ahead of the pressure sensor, thereby making it simpler to implement. However, this arrangement is not practical for medical device applications. Specifically, the placements of these two components are critical. If the two components (pressure sensor and exhaust valve) are mounted within a system enclosure, a long fluid connection line is necessary. This will result in greater volume added to the balloon chamber, making it more difficult to evacuate it of trapped air. It is critical to remove all air pockets from a balloon chamber prior to inflation, Otherwise, air will be introduced into the vessel if the balloon bursts. Having a larger volume will make the air evacuation process more time-consuming and difficult. In addition, a larger volume requires more fluid to fill. As a result, this setup is less efficient and increases overall procedure time.
Mounting the pressure switch and the exhaust solenoid valve directly to the catheter would solve the above issues, but would make the assembly very cumbersome to handle. This arrangement exposes dangling electrical components with their electrical wirings running from the catheter to the system. This setup is also expensive since the two components are disposable.
Regardless of the setups described above, a typical industrial purging system is not sensitive and quick to detect pressure spikes within the system because the detection/switching pressure of the pressure sensor has to be set at a value above the working pressure or balloon pressurization pressure. This is a result of two dynamics. First, pressurization of the balloon chamber is normally performed manually, resulting in variations in the pressure generated. The variations/fluctuations in pressure generated due to either user error or the equipment needs to be considered when determining the working pressure (i.e., balloon pressurization pressure). Second, the pressure sensor has a wide tolerance range at a set point. The lower value of the set point has to be used when determining the working pressure. Otherwise, the system might trigger a false alarm. When these two dynamics are considered together, the working pressure has to be below the low end of the pressure sensor's tolerance range minus the variations cause by the user. With the working pressure set at a value below the pressure sensor's trigger pressure, leaked gas needs additional time to accumulate enough volume within the balloon chamber to create a pressure rise reaching the detection/switching pressure of the pressure sensor. This will delay the response time, making the system less responsive in detecting gas leakage. However, reducing system response time is very critical in maximizing system performance.
There is currently no known in the market today for an automated balloon catheter fluid purging system, but there is a need, especially for catheters that have potential to release gas or foreign fluids into the human body/arterial vessel. Catheters that carry gas through a delivery system placed inside the human body can potentially break and leak gas. A balloon assembly covering the potential leakage section of the catheter can be used to capture leaked gas. However, balloon catheters of this type need a safety purging system to relieve buildup pressure preventing potential trauma. A balloon catheter is normally pressurized using saline to a predetermined working pressure. When foreign fluid leaks into the balloon chamber, its internal pressure raises.
An automated computer controlled purging system is needed because a manual monitoring and purging system does not provide the reliability, consistency, and instantaneous response needed to safeguard against abnormal pressure rises, and especially when there is a gas leakage from the gas delivery line. Pressurized gas can rapidly fill up a small confined balloon volume and cause significant pressure rise in short period of time. High pressure or over-pressurization can be detrimental to the patient:
a. Internal pressure adds stress on the component and causes it to expand. Over-pressuring the balloon, for example, can inflate the balloon to be larger than originally intended. This could stretch the patient's arterial wall beyond elastic limit and cause permanent damage.
b. High internal pressure will stress the material to its rupture point where it will burst open and release its fluid.
c. Unwanted fluid (such as pressurized gas, cryogen, etc.) can be released into the patient and cause trauma and even death.
d. A bursting balloon can cause physical damage to its surrounding (i.e., arterial wall) as the high pressure ruptures the balloon wall, pressing the torn material outward, and further stretching the surrounding wall, creating damages.
It is important to measure pressure instead of measuring flow rate or fluid accumulation level. To begin with, measuring pressure allows for instantaneous detection of leakage across the relief valve. Pressure creates stress within the material that bounds it, and should be controlled below a safe limit. In addition, pressure is easy to detect by using a high sensitivity and cost-effective pressure switch. Finally, detecting pressure is more cost-effective than detecting flow/leakage rate or fluid accumulation level, which requires a bulkier and more expensive flow meter or level indicator.